To the best of the applicant's knowledge, and prior to the citation of various prior art patents during the prosecution of the parent application, the most specific art appeared to be electrical units which were directly insertable into individual duct arms of forced air units, which were then employed to heat the air within the various arms of the duct system and which did not provide any central heating unit for the distribution of heat to the entire duct system, and which did not employ any arrangement for cooperation with the provided furnace and blower structure of the furnace. Further, to the best of the applicant's knowledge, no units existed which were primarily electrical heating operational units which provided control means for returning the unit to fossil fuel operation when the electrical supply is in a peak use condition or the cost of the electricity supplied is in a high rate condition.
It is common knowledge that power companies now may control use of electrical energy by various means. Some such means include timer devices for limitation of electrical useage during normal high power useage and also include signal devices which are controlled by power companies which will signal the electrically operated unit that power for its operation is being discontinued or alternatively is available. With applicant's device, the operation of a fossil fuel burning, forced air furnace is basically reversed. The unit is primarily an electric furnace except during peak power useage times, and during these peak power useages, the operation of the combination reverts to fossil fuel burning operation.
During the prosecution of the parent application, the following patents were cited by the Examiner: Martin, No. 2,893,639; Hinds, No. 2,458,268; Ferguson, No. 2,971,076; Lundbom, No. 3,061,706; Raymond, No. 3,098,145; Steinbruber, No. 2,242,630; Burgess, No. 2,759,708; Millspaugh, No. 3,084,741; and Taylor, No. 2,449,755.
Units disclosed by Lundbom, Steingruber, Burgess, and Taylor, are no more than simple electrical heating units, and there is no correlation between a simple electrical heating unit and a device which provides for operation in a preferred mode and switching from this preferred mode to a secondary operational mode.
Patents to Raymond and Millsbaugh disclose air conditioning systems which are utilized in conjunction with forced air systems, and again have no correlation to a unit which operates in conjunction with a fossil fuel burning furnace for heat generation. Obviously, when an air conditioning system is in operation, it is not desirable to switch between heating systems.
The patent to Martin is a combination of an electrical and fuel burning furnace, but on a general basis may be considered as totally opposite in operation to the unit of the applicant. In the Martin patent, the fuel burning heater remains inactive as long as the electrical supply is able to maintain the space at desired temperature. Should a drop in temperature result in the air to be heated, then the fuel burner takes over.
The Hinds patent is a simple structural disclosure which illustrates a staggering of heating elements and the provision of air guiding baffles.
It is the opinion of the applicant that these cited references do not properly serve to disclose, to one skilled in the art, the objects and advantages of the applicant's device, and likewise, they do not illustrate the structure of the device so as to prevent the patentability thereof.
It is therefore an object of the applicant's invention to provide a conversion unit for converting a normal fossil fuel burning, forced air furnace, into an electrically powered furnace wherein the fossil fuel operation is maintained, retained, and controlled for operation during those periods when electrical power is not available at a desired operating level or at a period when electrical power would be excessively expensive.
It is a further object of the applicant's invention to provide an electrically powered heating source for useage in close association to a fossil fuel burning, forced air furnace, which electrically powered heating source provides control means for utilization of various portions of the fossil fuel burning furnace, such as the air distribution blower.
It is still a further object of the applicant's invention to provide an electrically operated and energized heating system which is insertable into the ductwork of a fossil fuel burning, forced air heating system, wherein the electrically energized system is available for generation of heat at all off-peak electrical useage periods.
It is still a further object of the applicant's invention to provide an electrical heating system for use with a fossil fuel burning, forced air furnace, which forced air furnace may include an "A", air conditioning coil unit.
It is still a further object of the applicant's invention to provide control means for operation of an electrical heating system which operates in conjunction with a fossil fuel burning, forced air burning system, which prevents the energization of electrical heating elements of the electrical heating system while residual heat remains from prior operation of the fossil fuel burning portion of the combination.
It is yet another object of the applicant's invention to provide control mechanisms for an electrically powered heating system for use in conjunction with a fossil fuel burning, forced air heating system with such controls coordinating operation of the supplied elements as required.
These and other objects of the applicant's invention will more clearly appear from the following description made in association with the accompanying drawings.